So-called manual or countershaft or mechanical transmissions have a plurality of shift forks, which control the positioning of synchronizers within the transmission. The synchronizers establish the gear ratios between the transmission input shaft and the transmission output shaft. More recently, it has been proposed to employ synchronizer mechanisms or mechanical clutches with planetary type transmissions wherein two or more synchronizers are engaged simultaneously to establish the gear ratios within the planetary transmission.
Either of these types of transmissions, countershaft or planetary, have at least a reverse gear and planetary transmissions normally have a park gear. It is known to employ a mechanism for retarding or inhibiting the shift into a park or reverse condition when forward travel of the vehicle is underway. The inhibitor mechanisms are most often found directly on the manual shift tower and many of these require the use of a manual input such as a button or lever to unlock or disengage the inhibiting mechanism so that the reverse gear can be selected.